Seems like too much gas smell from the carbs.

[cleandan]

Are you running S&H air cleaners?  If yes, two things wrong with them out of the box. 

1 - Incredibly restrictive, which could cause it to run rich at WOT, pig rich, which would then come out of the exhaust.  Can't be fixed by jetting because you are choking it for air,  The fix is to go with a K&N element, which is taller if you have room to rey to get back some surface area.

I have tried to find paper elements that are taller,supposedly an S10 Chevy pickup works, but every brand I have had has been slightly big in OD to fit in the chrome cover.

2 - Repop Ford carbs vent tubes are very close to the lid and depending how you zonk them down can even partially block them.  Fix for this is to file/grind them to an angle toward each float bowl

I am running the Stelling and Hellings air filter housings.
I am running K&N airfilters too.
The float vents are angle cut to give room between the lid of the filter housing and the vent as well.

I wonder if a tube running between the vents might help. Much like the off roaders install to help with fuel spillage at steep angles.
The vent tube used on a Holley Truck Avenger carb may work here.
If nothing else this would help direct any vent purged fuel directly into the carb.

But, to be honest, I don't have evidence of fuel spillage anywhere around the carbs. Everything that should be dry, is dry.

I am running the secondaries slightly opened to help with idle.
Because of this I have specifically checked, multiple times, for any fuel pull over at idle from either the primary, or the secondary boosters...None, not even dampness.
I also have no vacuum signal from the ported vacuum tube at idle...indicating the transfer slot is not exposed.

I can slowly open the butterflies and watch the accelerator pump squirt, then the fuel start to flow as it should.

I do have the accelerator pumps set to squirt right away, but that squirt is not very much with smallish squirters, and a small pump cam...Heck, maybe a squirter is not squirting in the right direction and that is giving me the excess gas smell.
I'll check that just to be certain.

To everyone, thanks again for all the useful input.
I am not certain I will find the real issue, but every bit helps me get there if I can.

[machoneman]

Try the rubber tube trick between the vents for the heck of it. Slice a shallow groove through the tube's top at the apex for venting. Cheap & easy way to see if this helps. 

[My427stang]

I think you may want to give her a run with no air filters if you can

I am doing a deep breathing 457 with S&H filters, and we will use the K&N, but I have a gut feeling we will run out of air, even the taller K&Ns have less filter area than a comparable oval.  You could be going real rich when opening the 4 barrels and then smelling it after you come out of it

It'll be a bit before we hit the dyno, but I will share how much difference the a/f is with the S&H with taller K&Ns

Also, are you running any type of PCV?  Straight breathers allow some expansion, but not the same as pulling a vacuum at times other than than zero vacuum

[cleandan]

machoneman: the rubber hose trick is exactly what I am going to try.

my427stang: This 427 does not run a PCV system. It only has the rear intake stack breather.
Do you know if there is an airfilter style cover the size of the S&H cover?
This may get enough airflow to keep the A/F ratio correct at WOT.

[My427stang]

I have not researched it but I believe there is. Heard of other guys going that route

[Falcon67]

It's vents and pump fuel.  Modern pump fuel stinks, not like the sweet smell of real gasoline from the 60s.  The aromatics evap like crazy, especially with 10% ethanol.  I can't park the door car in the house garage because my wife - who can smell a cigarette smoker in a cattle truck a mile ahead - gets a headache shortly after.  The house is fairly well sealed but the fumes from the car creep in anyway.  Same in the shop - if I take it for a drive, when I put it up I switch off the pump and run the carbs as dry as possible.  The shop will still stink for 3~4 days.  IMHO the only real "cure" would be to adapt a full blown evap recovery system to the vehicle - piping it to the bowl vents, fuel cell vent, etc.

note - VP110 pure race gas does about the same, just the smell goes away after a couple of days less because there isn't any alcohol in it.

[machoneman]

"Modern pump fuel stinks, not like the sweet smell of real gasoline from the 60s."

Yes indeedy it does. I miss the old Sunoco 260 pump gas (wasn't it 102 octane?) that did smell damned good. Almost wanted to use it as aftershave! 

And yes, the smell of the modern pump gas no matter where its from or what octane rating it is smells terrible. Get some on your hands while fueling and ugh, I can hardly wait to wash it off.